Shape and proportions of shearheads



Sept. 17, 1963 v. KOBLER ETAL SHAPE AND PROPORTIONS 0F swamps FiledApril 28. 1961 Claims priority, application Switzerland Nov. 18, 1960 3Claims. (Cl. 30-34) This invention relates to dry shaving razors andmore particularly to a dry shaving razor of the type having at least oneexternal transversely slotted shearcomb and an elongate shearhead whichis circularly bent in longitudinal direction and has a movable innercutting blade.

In known razors of this type certain standard sizes have beenestablished for the radius of curvature, for the number of slots and thelength of chord of the shearhead, which were considered as optimum withrespect to manipulation of the razor and to efficiency of the shearhead.The external shearcomb surfaces thus usually have a length ranging from30 to 35 mm. and a number of slots within the limits of 28 and 32, whilethe radius of curvature is approximately 75 mm. The main advantage ofthis known type of shearhead construction has been found to consist inthat, during shaving, the shearcomb slightly depresses the particularskin portion and owing to its curvature is able to stretch the skin,which fact results in an erection of the hairs to a position in whichthey can be safely cut in close proximity to the skin. This quiteintelligible theory, however, has not been sufliciently confirmed inactual practice. Tests have shown that on the one hand the distancebetween the outer shearcomb ends and the middle tangential plane at thesummit of the curved shearcomb, which distance is determinative for thedepth of depression of the shearhead, is too small in known shearheadsto be able to cause sufficient stretching and thus tensioning of theskin. Frequently, some stretching of the often slack skin but withoutany elastic tension thereof only is obtained. On the other hand, thelength of the shearcomb and thus the surface of contact of the shearcombhave proved to be too small for maintaining, if at all obtained, anytension on the skin.

The object of the present invention is to provide a dry shaving razorhaving improved cutting characteristics. According to the invention, theexternal surface of the shearcomb extends through a sector angle of atleast 30 and the distance between the outer ends of this surface and atangential plane through the summit at the center of this shearcombsurface amounts to approximately twice the distance of the ends of amiddle section of the shearcomb from the tangential plane, which sectioncomprises at least 28 transverse slots.

The relatively large distance of the ends of the shearcomb surface fromthe middle tangential plane permits a correspondingly deep depression ofthe shearhead into the skin and thus an actual tensioning of the skinwhile the comparatively great length of the shearhead affords a surfaceof contact which results in the maintenance of the obtained tensioningof the skin.

The invention will now be more particularly described by way of examplewith reference to the accompanying drawing, in which a fragmentary viewof a dry shaving razor according to the invention is shown.

Referring to the drawing, numeral 1 represents the casing, serving ashandle of an electric driving motor. An elongate shearhead 2 comprisesan outer shearcomb 4 and a toothed movable internal cutting blade 4a,and is supported at one end of the casing 1. The casing 1 is slightlytapered towards the end carrying the shearhead, hair catching flaps 3adapted to be tilted downwards being linked to the lateral walls of thecasing 1;

tates Patent "ice the external surfaces of the flaps 3 are approximatelyin alignment with the associated lateral surfaces of the nontaperedportion of the casing. The arcuate elongate shearcomb 4 has continuoustransverse gaps 4b provided between webs 4c of roof-shaped, curvedcross-section. The open end faces 5 of the external shearcomb 4 divergeoutwardly on the cover plate of the tapered casing 1 from the bottom ofthe shearcomb at an angle, so that the shearcomb in its outer peripheryis considerably longer than at its bottom; in the example shown thisexternal length of the shearhead is even somewhat greater than themaximum width of the casing 1. The shape of the hair catching flaps 3 isselected to conform to the tapered portion of the casing 1 and theoutwardly open end faces 5 of the shearhead, whereby the flap end 3awhich abuts against the outer edge of these end faces of the shearheadpractically ends into a sharp edge.

The dimensions of the shearhead shown are selected so that this headcomprises for example 38 transverse gaps or slots 411, when having achord length S of the external shearcomb surface of approximately 45 mm.and a radius of curvature of about mm. (which data correspond to asector angle a of about 40). The distance a between the end of theexternal shearcomb surface and the tangential plane (3 through thelongitudinal center of this surface is approximately twice as great assaid distance b between the tangential plane 0 and the ends of a middleportion having the length L and comprising 30 transverse gaps 4b. Sinceneither the width of the transverse gaps 4b nor the width of thetransverse webs 40 can be made of any desired narrow size, the saidratio of distance of a=2b is approximately obtained in any case wherethe distance b is measured at the ends of a middle portion having anumber of gaps between 28 and 32 and the sector angle of the shearheadranges from 30 to 40.

The desired effect, however, will be also obtained in case the externalsurface of the shearcomb is not provided with transverse gaps extendinguntil its ends and in case not all transverse gaps representtransversely continuous slots; it is only necessary that the middlesection L has a number of cutting edges corresponding to the mentionedminimum number of gaps, since this middle section must undertake themain portion of the cutting work of the shearhead, while the endportions mainly cause the tensioning effect of the shearhead.

We claim:

1. A dry shaving razor having a casing serving as a handle; an elongateconvexly, circularly curved shearhead mounted on one end of said casingand being comprised of at least one external transversely slottedshearcomb, and a movable cutting blade Within said shearcomb, saidshearcomb having an upper surface having a radius of curvature of about75 mm., said shearcomb being comprised of a middle portion having alength ranging between about 30 to 35 millimeters and havingapproximately 218 to 32 of the transverse slots, and of two end portionsone at each end of said middle portion, the distance between the outerends of the surfaces of said end portions and a tangential plane throughthe center point of the topedge surface of said middle portion beingsubstantially twice the distance between the said tangential plane andthe ends of said middle portion of said shearcomb, whereby in shavingthe soft parts of the face said shearhead may be pressed against saidparts sufficiently strongly as to provide sufficient stretching of theskin with opening of the pores to attain satisfactory close shavingwithout the outer ends of the end portions of said shearhead coming incontact with the face.

2. A dry shaver according to claim 1, and in which the portion ofsaid-shearhead, adjacent said casing, is longer than the correspondingdimension of Said casing so as to have portions which extend beyond saidcasing at each end adjacent said handle, and hair-catching flapspivotally mounted on said handle at points spaced from said extendingportions and extending over the ends of said shearhead and havingportions extending beneath the extending portions of said shearhead,respectively.

3. A dry shaver according to claim 1, and in which said shearhead, atits ends, flares outwardly from the handle toward said upper surface ofsaid shearhead, and hair-catching flaps mounted on said handle at pointsspaced from said shearhead and extending over the flared ends of saidshearhead, respectively.

References Cited in the file of this patent UNITED STATES PATENTS MeyerDec. 29, 1936 Jones June 4, 1940 Jones June 23, 1942 Kobler et a1 July10, 1945 Kobler et a1 Sept. 23, 1952 Kobler Mar. 27, 1956 Kobler et al.Nov. 27, 1956 FOREIGN PATENTS Great Britain June 28, 1934 Germany Mar.19, 1953 Germany July 29, 1954

1. A DRY SHAVING RAZOR HAVING A CASING SERVING AS A HANDLE; AN ELONGATECONVEXLY, CIRCULARLY CURVED SHEARHEAD MOUNTED ON ONE END OF SAID CASINGAND BEING COMPRISED OF AT LEAST ONE EXTERNAL TRANSVERSELY SLOTTEDSHEARCOMB, AND A MOVABLE CUTTING BLADE WITHIN SAID SHEARCOMB, SAIDSHEARCOMB HAVING AN UPPER SURFACE HAVING A RADIUS OF CURVATURE OF ABOUT75 MM., SAID SHEARCOMB BEING COMPRISED OF A MIDDLE PORTION HAVING ALENGTH RANGING BETWEEN ABOUT 30 TO 35 MILLIMETERS AND HAVINGAPPROXIMATELY 28 TO 32 OF THE TRANSVERSE SLOTS, AND OF TWO END PORTIONSONE AT EACH END OF SAID MIDDLE PORTION, THE DISTANCE BETWEEN THE OUTERENDS OF THE SURFACES OF SAID END PORTIONS AND A TANGENTIAL PLANE THROUGHTHE CENTER POINT OF THE TOP EDGE SURFACE OF SAID MIDDLE PORTION BEINGSUBSTANTIALLY TWICE THE DISTANCE BETWEEN THE SAID TANGENTIAL PLANE ANDTHE ENDS OF SAID MIDDLE PORTION OF SAID SHEARCOMB, WHEREBY IN SHAVINGTHE SOFT PARTS OF THE FACE SAID SHEARHEAD MAY BE PRESSED AGAINST SAIDPARTS SUFFICIENTLY STRONGLY AS TO PROVIDE SUFFICIENT STRETCHING OF THESKIN WITH OPENING OF THE PORES TO ATTAIN SATISFACTORY CLOSE SHAVINGWITHOUT THE OUTER ENDS OF THE END PORTIONS OF SAID SHEARHEAD COMING INCONTACT WITH THE FACE.